An image sensor is a semiconductor device that may convert an optical image into an electrical signal. The image sensor may be divided into a charge coupled device (CCD) image sensor and a CMOS image sensor.
The CCD image sensor may have a plurality of metal-oxide-silicon (MOS) capacitors spatially located in very close proximity to each other and which store charger carriers are stored and transferred. The CMOS image sensor may adopt a switching manner including MOS transistors having corresponding pixels. The MOS transistors may be formed using a complementary MOS (CMOS) technique using a control circuit and a signal processing circuit on and/or over a peripheral circuit and then sequentially detecting outputs using them.
The CMOS image sensor may convert information of an object into an electrical signal and can be configured of signal processing chips having a photodiode. One chip may be combined with an amplifier, an analog/digital converter, an internal voltage generator, a timing generator, and a digital logic, etc. to provide advantages such as space, power, and reduced costs.
The CMOS image sensor may have advantages of its ability to be cheaply mass produced and obtain high integration using an etching process of a silicon wafer when compared to the charge coupled device (CCD) image sensor.
The CMOS image sensor can include a microlens, a planarization layer, a color filter array, and a photodiode. The color filter array may divide the incident light into three primary colors (e.g., red, green, and blue) to transfer them into the photodiode. The microlens may perform the function of condensing light into the photodiode. The photo diode may perform the function converting light into an electrical signal.
As illustrated in example FIG. 1A, a method of manufacturing a microlens may include in first step (S1) coating thermal resin 1 on and/or over a substrate. In step 2 (S2), blue color filter 2 may then be formed on and/or over thermal resin 1. In step 3 (S3), green color filter 3 may then be formed over thermal resin 1 and adjacent blue color filter 2. In step 4 (S4), red color filters 4 may then be formed on and/or over thermal resin 1 and adjacent blue color filter 2 and green color filter 3.
In step 5 (S5), planarization layer 5 may then be formed on and/or over thermal resin 1 including blue color filter 2, green color filter 3 and red color filters 4 through a planarization process. In step 6 (S6), an oxygen (O2) ashing process may then be performed to remove residue. In step 7 (S7), a plurality of microlens 7 may then be formed on and/or over planarization layer 5 and spatially correspond to a respective color filter. In step 8 (S8), bleaching (BLCH) process is performed on microlens 7. The step of forming the microlens may serve to lower the viscosity of a photoresist (PR) formed by controlling the focus of an exposure equipment, having excellent transmittance, by way of a reflow process, and manufactures a circular lens by means of weight.
If such a manufacturing method is applied, it may have problems of consistently forming the curved surface for the microlens, and thus, the efficiency of producing CMOS image sensors may be reduced. Moreover, the microlens may have problems of adequately condensing light since the microlenses are spaced a predetermined distance.